The present invention relates to a process for the production of a non-aqueous electrolyte battery such as polymer battery.
A polymer battery is a non-aqueous electrolyte battery comprising a positive electrode and a negative electrode integrally bonded to each other with a polymer layer impregnated with an electrolyte optionally with a separator interposed therebetween. Conventional processes for the production of the polymer battery will be described below.
Referring to a first process for the production of the polymer battery, a polymer material is dissolved in a solvent. The solution is then applied to the surface of a positive electrode, a negative electrode or a separator. The positive electrode and the negative electrode are laminated with the separator interposed therebetween, and then optionally wound to prepare an electricity-generating element. Subsequently, the electricity-generating element is dried to evaporate the solvent so that a polymer layer is formed, causing the positive electrode, the negative electrode and the separator to be bonded to each other. Subsequently, the electricity-generating element is received into a battery case. Into the battery case is then injected an electrolyte to impregnate the electrodes and the polymer layer with the electrolyte. Thus, a polymer battery is produced.
Referring to a second process for the production of the polymer battery, a positive electrode and a negative electrode are laminated with a polymer film interposed therebetween, and then optionally wound to prepare an electricity-generating element. Subsequently, the electricity-generating element is heated so that the polymer film is melted to form a polymer layer with which the positive electrode and the negative electrode are bonded to each other. Subsequently, the electricity-generating element is received into a battery case. An electrolyte is then injected into the battery case so that the polymer layer provided between the positive electrode and the negative electrode is impregnated with the electrolyte to prepare a polymer battery. (In this production process, a separator may be interposed between the positive electrode and the negative electrode.).
Referring to a third process for the production of the polymer battery (disclosed in JP-A-10-255849), a polymer film is prepared on the surface of a support. The polymer film is then impregnated with an electrolyte. Subsequently, the polymer film is provided interposed between a positive electrode and a negative electrode. These layers are then laminated, and then optionally wound to prepare an electricity-generating element.
Alternatively, a polymer film is prepared on the surface of a positive electrode or a negative electrode. The polymer film is then impregnated with an electrolyte to form a polymer layer. Subsequently, the electrode is laminated with the other electrode with the polymer layer interposed therebetween, and then optionally wound to prepare an electricity-generating element.
Subsequently, these electricity-generating elements are each heated under pressure so that the polymer film or polymer layer is partly melted to bond the positive electrode and the negative electrode to each other. These electricity-generating elements are each then received into a battery case to prepare a polymer battery.
However, the aforementioned conventional production processes have the following disadvantages.
In accordance with the first and second production processes, the electricity-generating element is impregnated with the electrolyte after the bonding of the positive electrode and the negative electrode with a polymer layer. In other words, the polymer layer has already been kept in close contact with the electrodes without any gap before the injection of the electrolyte. This makes it possible for the electrolyte to penetrate only into the edge of the polymer layer, requiring much time for the electrolyte to penetrate into the entire part of the polymer layer deep inside thereof. As a result, subsequent steps such as initial charge are delayed, deteriorating the battery productivity to disadvantage. This problem will be further described with reference to an example in connection with FIG. 4. FIG. 4 illustrates an electricity-generating element comprising a positive electrode 1 and a negative electrode 2 bonded to each other with the interposition of a separator 3 coated with a polymer layer 4 on both sides thereof produced by the first or second production process. When an electrolyte is injected into the battery case after bonding, the electrolyte can penetrate into the electricity-generating element only through the edge of the polymer layer 4 exposed at the positive electrode 1 and the negative electrode 2 as shown by the arrow A in FIG. 4. Similarly, the electrolyte can penetrate into the active material of the positive electrode 1 and the negative electrode 2 only through the edge thereof.
The third production process is disadvantageous in that the gel-like polymer film or layer the strength of which is deteriorated due to impregnation with the electrolyte needs to be handled, making it difficult to produce the battery. In other words, the operation involving the conveyance of the gel-like polymer film and the disposition of the gel-like polymer film between the positive electrode and the negative electrode, the operation involving the conveyance of the electrodes having a gel-like polymer layer formed thereon, the operation involving the lamination or winding of these layers, etc. cannot be easily carried out, making it difficult to produce the battery. Further, since the amount of the electrolyte to be injected is determined by the content of electrolyte in the polymer layer or polymer film, making it impossible to inject the electrolyte into the battery case invariably in a predetermined amount. Moreover, since no separator is interposed between the positive electrode and the negative electrode, internal shortcircuiting can easily occur in the battery.
The invention has been worked out to cope with such circumstances. An aim of the invention is to provide a process for the production of a non-aqueous electrolyte battery which comprises heating the electricity-generating element under pressure after the injection of the electrolyte so that the electrodes are bonded to each other with the polymer layer, allowing the electricity-generating element to be rapidly impregnated with the electrolyte and hence facilitating the production of the battery.
The invention lies in a process for the production of a non-aqueous electrolyte battery comprising the following steps. In other words, the process for the production of a non-aqueous electrolyte battery of the invention comprises a polymer layer forming step of forming a polymer layer on at least one side of at least one of a positive electrode, a negative electrode and a separator and an electricity-generating element preparing step of laminating or winding the positive electrode, the negative electrode and the separator to prepare an electricity-generating element. The process for the production of a non-aqueous electrolyte battery of the invention further comprises battery preparing step of receiving the electricity-generating element in a battery case, injecting an electrolyte into the battery case and then hermetically sealing the battery case to prepare a non-aqueous electrolyte battery and a heating and cooling step of heating and cooling the non-aqueous electrolyte battery while the battery case is under pressure.
In accordance with the present invention, the electrolyte is injected into the battery case at the battery preparing step which is before the bonding of the electricity-generating element at the heating and cooling step. Accordingly, a desired gap between the polymer layer and the electrode or the like is secured before the injection of the electrolyte into the battery case, allowing the electrolyte to penetrate into the inside of the electricity-generating element through the gap and hence allowing the electricity-generating element to be rapidly impregnated with the electrolyte from the entire surfaces of the polymer layer and the electrodes into the inside thereof. As a result, subsequent steps such as initial charge can be rapidly carried out, improving the battery productivity.